System and method of controlling a power converter having an LC tank coupled between a switching network and a transformer winding

Abstract

A method of operating a converter includes: charging an LC tank coupled between a switching network and a primary winding of a transformer for a first period of time by connecting the LC tank to one or more input capacitors via the switching network, where the switching network includes a first half-bridge coupled between a first supply terminal and a center node, and a second half-bridge coupled between the center node and a second supply terminal; preventing energy transfer from the primary winding of the transformer to a secondary winding of the transformer during the charging of the LC tank; and after charging the LC tank, discharging the LC tank for a second period of time by disconnecting a terminal of the LC tank from the one or more input capacitors.

What is claimed is: 
     
       1. A method of operating a converter comprising:
 charging an LC tank coupled between a switching network and a primary winding of a transformer for a first period of time by connecting the LC tank to one or more input capacitors via the switching network, wherein the switching network comprises a first half-bridge coupled between a first supply terminal and a center node, and a second half-bridge coupled between the center node and a second supply terminal, and wherein a portion of the first half-bridge and a portion of the second half-bridge are configured to provide a current recirculation mode with the LC tank; 
 preventing energy transfer from the primary winding of the transformer to a secondary winding of the transformer during the charging of the LC tank; and 
 after charging the LC tank, discharging the LC tank for a second period of time by disconnecting a terminal of the LC tank from the one or more input capacitors. 
 
     
     
       2. The method of  claim 1 , wherein preventing energy transfer from the primary winding of the transformer to the secondary winding of the transformer during the charging the LC tank comprises reverse biasing a diode in series with the secondary winding of the transformer. 
     
     
       3. The method of  claim 1 , wherein connecting the LC tank to the one or more input capacitors comprises turning on one or more transistors of the switching network with zero-voltage switching (ZVS) for a third period of time after disconnecting the terminal of the LC tank from the one or more input capacitors. 
     
     
       4. The method of  claim 3 , further comprising determining the third period of time based on a voltage of the one or more input capacitors. 
     
     
       5. The method of  claim 1 , wherein discharging the LC tank comprises turning on one or more transistors of the switching network with ZVS for a fourth period of time after disconnecting the terminal of the LC tank from the one or more input capacitors. 
     
     
       6. The method of  claim 1 , wherein
 the disconnecting the terminal of the LC tank from the one or more input capacitors transfers a first energy to the secondary winding of the transformer; 
 the first period of time determines the first energy; and 
 a resonance frequency of the LC tank determines the second period of time. 
 
     
     
       7. The method of  claim 6 , further comprising controlling the first period of time based on a PWM signal. 
     
     
       8. The method of  claim 1 , further comprising:
 when a voltage of an output terminal of the converter is higher than a predetermined value, transferring energy from the output terminal of the converter into a storage device; and 
 when the voltage of the output terminal of the converter is lower than the predetermined value, transferring energy from the storage device into the output terminal. 
 
     
     
       9. The method of  claim 1 , further comprising regulating a voltage of an output terminal of the converter by transferring energy between the output terminal and a storage device via a bidirectional converter. 
     
     
       10. The method of  claim 1 , wherein the one or more input capacitors comprises a first input capacitor and a second input capacitor, the method further comprising:
 receiving a rectified AC voltage via the one or more input capacitors; and 
 when the rectified AC voltage is a rectified low-line voltage, charging the LC tank comprises simultaneously transferring energy from the first input capacitor and the second input capacitor into the LC tank, and 
 when the rectified AC voltage is a rectified high-line voltage, charging the LC tank comprises transferring energy from the first input capacitor into the LC tank or transferring energy from the second input capacitor into the LC tank alternatively, without simultaneously transferring energy from the first input capacitor and second input capacitor into the LC tank. 
 
     
     
       11. The method of  claim 10 , further comprising:
 when the rectified AC voltage is the rectified high-line voltage, charging the LC tank further comprises 
 transferring energy from the first input capacitor into the LC tank for a fifth period of time during a first switching cycle, and 
 transferring energy from the second input capacitor into the LC tank for a sixth period of time during a second switching cycle after the first switching cycle. 
 
     
     
       12. The method of  claim 11 , further comprising:
 monitoring a voltage of an intermediate node coupled between the first input capacitor and the second input capacitor; 
 determining the fifth period of time based on the voltage of the intermediate node; and 
 determining the sixth period of time based on the voltage of the intermediate node. 
 
     
     
       13. The method of  claim 10 , further comprising generating the rectified AC voltage from an AC voltage with a bridge rectifier, wherein:
 when the rectified AC voltage is the rectified low-line voltage, the AC voltage is a low-line voltage comprising a root-mean-square (RMS) voltage between 85 V and 140 V; and 
 when the rectified AC voltage is the rectified high-line voltage, the AC voltage is a high-line voltage comprising an RMS voltage between 200V and 270V. 
 
     
     
       14. A converter comprising a controller configured to:
 charge an LC tank coupled between a switching network and a primary winding of a transformer for a first period of time by connecting the LC tank to one or more input capacitors by controlling transistors of the switching network, wherein the switching network comprises a first half-bridge coupled between a first supply terminal and a center node, and a second half-bridge coupled between the center node and a second supply terminal, and wherein a portion of the first half-bridge and a portion of the second half-bridge are configured to provide a current recirculation mode with the LC tank; 
 prevent energy transfer from the primary winding of the transformer to a secondary winding of the transformer during the charging the LC tank by controlling a first transistor in series with the secondary winding of the transformer; and 
 after charging the LC tank, discharge the LC tank for a second period of time to transfer a first energy to the secondary winding of the transformer by 
 disconnecting a terminal of the LC tank from the one or more input capacitors by turning off two transistors of the switching network. 
 
     
     
       15. The converter of  claim 14 , wherein preventing energy transfer from the primary winding of the transformer to the secondary winding of the transformer during the charging the LC tank comprises turning off the first transistor. 
     
     
       16. The converter of  claim 15 , wherein the controller is further configured to turn on the first transistor a fourth period of time after current begins flowing through a body diode of the first transistor. 
     
     
       17. The converter of  claim 14 , wherein the controller is further configured to control the first period of time based on a PWM signal. 
     
     
       18. The converter of  claim 17 , wherein the controller is further configured to:
 control transistors of a bidirectional converter stage coupled between an output terminal and a storage device to regulate a voltage at the output terminal, wherein the output terminal is coupled to the secondary winding of the transformer; and 
 control transistors of the switching network to regulate a voltage at a terminal of the storage device. 
 
     
     
       19. The converter of  claim 18 , wherein the controller is further configured to:
 control transistors of the bidirectional converter stage to buck-convert from the output terminal to the terminal of the storage device when the voltage at the output terminal is above a predetermined threshold; and 
 control transistors of the bidirectional converter stage to boost from the terminal of the storage device to the output terminal when the voltage at the output terminal is below the predetermined threshold. 
 
     
     
       20. The converter of  claim 18 , wherein transistors of the switching network switch at a lower frequency than transistors of the bidirectional converter stage. 
     
     
       21. The converter of  claim 18 , further comprising:
 the LC tank; 
 the switching network; 
 the transformer; 
 the bidirectional converter stage; and 
 the first transistor. 
 
     
     
       22. The converter of  claim 14 , wherein the one or more input capacitors are coupled between an AC power source producing an AC voltage and the switching network, the one or more input capacitors comprising a first input capacitor and a second input capacitor, the controller further configured to:
 when the AC voltage is a low-line voltage, control transistors of the switching network to simultaneously transfer energy from the first input capacitor and the second input capacitor into the LC tank; and 
 when the AC voltage is a high-line voltage, control transistors of the switching network to transfer energy from the first input capacitor into the LC tank or the second input capacitor into the LC tank, without simultaneously transferring energy from the first input capacitor and second input capacitor into the LC tank. 
 
     
     
       23. The converter of  claim 22 , wherein the controller is further configured to:
 monitor a rectified voltage generated by a bridge rectifier coupled between the AC power source and the one or more input capacitors; and 
 determine whether the AC voltage is the high-line voltage or the low-line voltage based on the monitoring the rectified voltage. 
 
     
     
       24. The converter of  claim 22 , wherein the controller is further configured to:
 when the AC voltage is the high-line voltage,
 control transistors of the switching network to transfer energy from the first input capacitor into the LC tank for a fourth period of time during a first switching cycle, and 
 control transistors of the switching network to transfer energy from the second input capacitor into the LC tank for a fifth period of time during a second switching cycle after the first switching cycle. 
 
 
     
     
       25. The converter of  claim 24 , wherein the controller is further configured to:
 monitor a voltage of an intermediate node coupled between the first input capacitor and the second input capacitor; and 
 determine the fourth period of time based on the voltage of the intermediate node.